Bethe–Feynman formula

The Bethe–Feynman efficiency formula, a simple method for calculating the yield of a fission bomb, was first derived in 1943 after development in 1942. Aspects of the formula are speculated to be secret restricted data.

Related formula

• a = internal energy per gram
• b = growth rate
• c = sphere radius

$a\approx (bc{)}^{2}f$

A numerical coefficient would then be included to create the Bethe–Feynman formula—increasing accuracy by more than an order of magnitude.

$E_{f}f=\left(\frac{E_2}{\gamma -1}\right)\cdot {\alpha }_{max}^2\cdot R_{crit}^2\cdot \left(\frac{\delta }{1-\delta }\right)\cdot \left(\frac{2+3\delta }{2}\right)$

where γ is the thermodynamic exponent of a photon gas, Template:Math is the prompt energy density of the fuel, α is VTemplate:Sub (neutron velocity) / λTemplate:Sub (total reaction mean free path), RTemplate:Sub is the critical radius and 𝛿 is the excess supercritical radius Template:Math.

See also

• Richard Feynman
• Hans Bethe
• Robert Serber

References

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